// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/base/models/list_selection_model.h"

#include <algorithm>
#include <valarray>

#include "base/logging.h"

namespace ui {

// static
const int ListSelectionModel::kUnselectedIndex = -1;

static void IncrementFromImpl(int index, int* value)
{
    if (*value >= index)
        (*value)++;
}

static bool DecrementFromImpl(int index, int* value)
{
    if (*value == index) {
        *value = ListSelectionModel::kUnselectedIndex;
        return true;
    }
    if (*value > index)
        (*value)--;
    return false;
}

ListSelectionModel::ListSelectionModel()
    : active_(kUnselectedIndex)
    , anchor_(kUnselectedIndex)
{
}

ListSelectionModel::~ListSelectionModel()
{
}

void ListSelectionModel::IncrementFrom(int index)
{
    // Shift the selection to account for the newly inserted tab.
    for (SelectedIndices::iterator i = selected_indices_.begin();
         i != selected_indices_.end(); ++i) {
        IncrementFromImpl(index, &(*i));
    }
    IncrementFromImpl(index, &anchor_);
    IncrementFromImpl(index, &active_);
}

void ListSelectionModel::DecrementFrom(int index)
{
    for (SelectedIndices::iterator i = selected_indices_.begin();
         i != selected_indices_.end();) {
        if (DecrementFromImpl(index, &(*i)))
            i = selected_indices_.erase(i);
        else
            ++i;
    }
    DecrementFromImpl(index, &anchor_);
    DecrementFromImpl(index, &active_);
}

void ListSelectionModel::SetSelectedIndex(int index)
{
    anchor_ = active_ = index;
    selected_indices_.clear();
    if (index != kUnselectedIndex)
        selected_indices_.push_back(index);
}

bool ListSelectionModel::IsSelected(int index) const
{
    return std::find(selected_indices_.begin(), selected_indices_.end(), index) != selected_indices_.end();
}

void ListSelectionModel::AddIndexToSelection(int index)
{
    if (!IsSelected(index)) {
        selected_indices_.push_back(index);
        std::sort(selected_indices_.begin(), selected_indices_.end());
    }
}

void ListSelectionModel::RemoveIndexFromSelection(int index)
{
    SelectedIndices::iterator i = std::find(selected_indices_.begin(),
        selected_indices_.end(), index);
    if (i != selected_indices_.end())
        selected_indices_.erase(i);
}

void ListSelectionModel::SetSelectionFromAnchorTo(int index)
{
    if (anchor_ == kUnselectedIndex) {
        SetSelectedIndex(index);
    } else {
        int delta = std::abs(index - anchor_);
        SelectedIndices new_selection(delta + 1, 0);
        for (int i = 0, min = std::min(index, anchor_); i <= delta; ++i)
            new_selection[i] = i + min;
        selected_indices_.swap(new_selection);
        active_ = index;
    }
}

void ListSelectionModel::AddSelectionFromAnchorTo(int index)
{
    if (anchor_ == kUnselectedIndex) {
        SetSelectedIndex(index);
    } else {
        for (int i = std::min(index, anchor_), end = std::max(index, anchor_);
             i <= end; ++i) {
            if (!IsSelected(i))
                selected_indices_.push_back(i);
        }
        std::sort(selected_indices_.begin(), selected_indices_.end());
        active_ = index;
    }
}

void ListSelectionModel::Move(int from, int to)
{
    DCHECK_NE(to, from);
    bool was_anchor = from == anchor_;
    bool was_active = from == active_;
    bool was_selected = IsSelected(from);
    if (to < from) {
        IncrementFrom(to);
        DecrementFrom(from + 1);
    } else {
        DecrementFrom(from);
        IncrementFrom(to);
    }
    if (was_active)
        active_ = to;
    if (was_anchor)
        anchor_ = to;
    if (was_selected)
        AddIndexToSelection(to);
}

void ListSelectionModel::Clear()
{
    anchor_ = active_ = kUnselectedIndex;
    SelectedIndices empty_selection;
    selected_indices_.swap(empty_selection);
}

void ListSelectionModel::Copy(const ListSelectionModel& source)
{
    selected_indices_ = source.selected_indices_;
    active_ = source.active_;
    anchor_ = source.anchor_;
}

bool ListSelectionModel::Equals(const ListSelectionModel& rhs) const
{
    return active_ == rhs.active() && anchor_ == rhs.anchor() && selected_indices() == rhs.selected_indices();
}

} // namespace ui
